1. Field of the Invention
This invention relates to a plasma display panel (PDP), and more particularly to a radio frequency driving circuit and a switching method thereof that are capable of switching a radio frequency signal to be adaptive for a radio frequency PDP driving.
2. Description of the Related Art
Recently, a plasma display panel (PDP) feasible to the fabrication of large-scale panel has been available for a flat panel display device. The PDP includes discharge cells corresponding to color pixels of matrix type and controls a discharge interval of each discharge cell to display a picture. More specifically, after the PDP selected discharge cells to be displayed by an address discharge, it allows a discharge to be maintained in a desired discharge interval at the selected discharge cells. Thus, in the discharge cells, a vacuum ultraviolet ray generated during the sustaining discharge radiates a fluorescent material to emit a visible light. In this case, the PDP controls a discharge-sustaining interval, that is, a sustaining discharge frequency of the discharge cells to implement a gray scale required for an image display. As a result, the sustaining discharge frequency becomes an important factor for determining the brightness and a discharge efficiency of the PDP. For the purpose of performing such a sustaining discharge, a sustaining pulse having a frequency of 200 to 300 kHz and a width of about 10 to 20 xcexcs has been used in the prior art. However, the sustaining discharge is generated only once at a extremely short instant per the sustaining pulse by responding to the sustaining pulse; while it is wasted for a step of forming a wall charge and a step of preparing the next sustaining discharge at the remaining major time. For this reason, the conventional three-electrode, face-discharge, and AC PDP has a problem in that, since a real discharge interval is very short in comparison to the entire discharge interval, the brightness and the discharge efficiency become low.
In order to solve such a problem of low brightness and low discharge efficiency, we has suggested a method of utilizing a radio frequency discharge employing a radio frequency signal of hundreds of MHz as a display discharge. In the case of the radio frequency discharge, electrons perform an oscillating motion by the radio frequency signal to sustain the display discharge in a time interval when the radio frequency signal is being applied. More specifically, when a radio frequency signal with a continuously alternating polarity is applied to any one of the two opposite electrodes, electrons within the discharge space are moved toward one electrode or the other electrode depending on the polarity of the voltage signal. If the polarity of a radio frequency voltage signal having been applied to the electrode before the electrons arrive at the electrode is changed when electrons are moved into any one electrode, then the electrons has a gradually decelerated movement speed in such a manner to allow their movement direction to be changed toward the opposite electrode. The polarity of the radio frequency voltage signal having been applied to the electrode before the electrons within the discharge space arrive at the electrode is changed as described, so that the electrons make an oscillating motion between the two electrodes. Accordingly, when the radio frequency voltage signal is being applied, the ionization, the excitation and the transition of gas particles are continuously generated without extinction of electrons. The display discharge is sustained during most discharge time, so that the brightness and the discharge efficiency of the PDP can be improved. Such a radio frequency discharge has the same physical characteristic as a positive column in a glow discharge structure.
FIG. 1 is a perspective view showing the structure of a discharge cell of the above-mentioned radio frequency PDP employing a radio frequency discharge. In FIG. 1, the discharge cell 26 includes radio frequency electrodes 12 provided on an upper substrate 10, data electrodes 16 and scanning electrodes 20 provided on a lower substrate 14 in such a manner to be perpendicular to each other, and barrier ribs 22 provided between the upper substrate 10 and the lower substrate 14. The radio frequency electrodes 12 apply a radio frequency signal. The data electrodes 16 apply a data pulse for selecting cells to be displayed. The scanning electrodes 20 are provided in opposition to the radio frequency electrodes 12 in such a manner to be used as opposite electrodes of the radio frequency electrodes 12. Between the data electrodes 16 and the scanning electrodes 20 is provided a dielectric layer 18 for the charge accumulation and the isolation. The barrier ribs 22 shut off an optical interference between the cells. In this case, the barrier ribs 22 are formed into a lattice structure closed on every side for each discharge cell so as to isolate the discharge space. This is because it is difficult to isolate a plasma for each cell unlike the existent face-discharge due to the opposite discharge generated between the radio frequency electrodes 12 and the scanning electrodes 20. Also, the barrier ribs 22 have a more enlarged height than the conventional barrier ribs for the sake of providing a smooth radio frequency discharge between the scanning electrodes 20 and the radio frequency electrodes 12. A fluorescent material 24 is coated on the surface of the barrier rib 22 to emit a visible light with an inherent color by a vacuum ultraviolet ray generated during the radio frequency discharge. The discharge space defined by the upper substrate 10, the lower substrate 14 and the barrier ribs 22 is filled with a discharge gas.
As shown in FIG. 2, the discharge cells 26 having the configuration as described above are positioned at each intersection among data electrode lines X1 to Xm, scanning electrode lines Y1 to Yn and radio frequency electrode lines RF. In FIG. 2, the data electrode lines X1 to Xm consist of the data electrodes 16 of the discharge cells 26. The scanning electrode lines Y1 to Yn consist of the scanning electrodes 20, and the radio frequency electrode lines RF consist of radio frequency electrodes 12.
The discharge cell 26 of FIG. 1 is driven a driving waveform as shown in FIG. 3. A radio frequency pulse RFP more than tens of MHz is continuously applied to the radio frequency electrode 12. At an A region in which a data pulse DP is applied to the address electrode 16 and a scanning pulse SP is applied to the scanning electrode 20, an address discharge is generated by the voltage difference Vd+Va. By this address discharge, charged particles are produced at the discharge space. These charged particles make a radio frequency discharge by a radio frequency pulse RFP applied to the radio frequency electrode 12 and a center voltage Vc of a radio frequency voltage applied constantly to the scanning electrode 20. In this case, an ultraviolet ray generated by the radio frequency discharge radiates the fluorescent material 24 to emit a visible light. At a C region in which an erasing pulse EP is applied to the scanning electrode 20, the charged particles are vanished by an erasure voltage Ve to stop the radio frequency discharge.
As described above, the conventional radio frequency PDP applies the radio frequency signal continuously to thereby initiate the radio frequency discharge by the charged particles produced by the address discharge and the radio frequency signal and stop the radio frequency discharge by the erasure pulse EP. The gray scale is implemented by differently setting a time at which the erasure pulse EP is applied to control the radio frequency discharge interval, that is, the discharge-sustaining interval. If the radio frequency signal is continuously applied in the remaining interval except for the radio frequency discharge interval, however, then problems such as signal interference, noise and miss-discharge, etc. may be generated. In order to prevent these problems, it is necessary to switch the radio frequency signal to provide it only in the radio frequency discharge interval. However, it is difficult to switch the radio frequency signal requiring more than hundreds of volt (V), for the sake of providing the radio frequency discharge, at a rapid time rate such as the radio frequency discharge interval.
More specifically, a radio frequency circuit of the PDP for switching a radio frequency signal can be configured as shown in FIG. 4. Referring to FIG. 4, the radio frequency circuit includes a radio frequency generator 30 for generating a radio frequency signal, an amplifier 34 for amplifying the radio frequency signal from the radio frequency generator 30, and an impedance matcher 37 connected between the amplifier 34 and a panel 38. The radio frequency generator 30 generates a low level of radio frequency pulse and outputs it to the amplifying unit 35. The amplifying unit 35 consists of the amplifier 34 and a peak detector 36. The amplifying unit 35 amplifies the radio frequency pulse from the radio frequency generator 30 into a power required for the radio frequency discharge and output it. The peak detector 36 detects a peak-to-peak value PPrf from the radio frequency pulse from the amplifier 34 and feeds it back into the amplifier 34 thereby allowing the amplifier 34 to amplify and output the radio frequency pulse into a certain power. The impedance matcher 37 matches an impedance at the output terminal of the amplifying unit 35 with an impedance of the panel 38, thereby applying a maximum power of radio frequency signal to the radio frequency electrode 12. Generally, an incident wave and a reflective wave co-exist in the radio frequency circuit, and a power superposed with the incident wave and the reflective wave is applied to the radio frequency electrode 12 of the panel 38. Thus, to apply a maximum power by the impedance matching means to allow an incident wave to be applied to the radio frequency electrode 12 as it is by a minimization of a reflective wave.
The switch 32 switches the radio frequency signal from the radio frequency generator 30 in accordance with a switching signal SWS, as shown in FIG. 5, inputted via an input line 31. Referring to FIG. 5, the switch 32 is turned off in address intervals (AP1, AP2, AP3, . . . ) of each sub-field (SF1, SF2, SF3, . . . ) at which the input switching signal SWS has a low level to thereby shut off the radio frequency pulse from the radio frequency generator 30. On the other hand, the switch 32 is turned on only in discharge-sustaining intervals (SP1, SP2, SP3, . . . ) of each sub-field (SF1, SF2, SF3, . . . ) at which the input switching signal SWS has a high level to thereby apply the radio frequency pulse from the radio frequency generator 30 to the amplifier 34. In this case, the switch 32 must generate a radio frequency signal in a soft start manner so as to assure a safety of the entire PDP system. This is because of a damage of circuit caused by a rush current when a high voltage of radio frequency signal is rapidly generated. Accordingly, the switch 32 has to slowly increase the radio frequency voltage in a range in which the rush current is minimized. In such a soft start method, however, a time of at least tens of to hundreds of xcexcs is wasted for a rising time until the radio frequency signal arrives at a normal level.
As described above, in the conventional radio frequency signal switching method, a considerably long time is wasted for a rising time when the radio frequency signal is increased into a normal level required for the radio frequency discharge after the generation thereof. Accordingly, the radio frequency discharge interval is relatively shortened to have a bad influence on the guarantee of display time regarded as a most important factor in the PDP. In other words, the conventional radio frequency signal switching method is not applicable to a PDP required to switch a radio frequency signal within a very short time for the purpose of an implementation of gray scale as it is.
Accordingly, it is an object of the present invention to provide a radio frequency driving circuit and a radio frequency signal switching method thereof that is capable of sufficiently assuring a radio frequency discharge interval by switching a radio frequency signal in a rapid time interval suitably for a PDP driving.
A further object of the present invention is to provide a radio frequency driving circuit and a radio frequency signal switching method thereof that is capable of stably driving a PDP employing a radio frequency signal by switching the radio frequency signal to apply the same to a panel only in a display interval.
In order to achieve these and other objects of the invention, a method of switching a radio frequency signal in a plasma display panel according to one aspect of the present invention includes applying a turning-on signal before the radio frequency signal is completely erased by applying a turning-off signal to a radio frequency generator, thereby generating the radio frequency signal.
A driving circuit for a plasma display panel according to another aspect of the present invention includes radio frequency generating means for generating a radio frequency signal; and impedance matching means for matching an impedance of the radio frequency generating means with that of the plasma display panel and varying the matched impedance to switch the radio frequency signal.
A method of switching a radio frequency signal in a plasma display panel employing the radio frequency discharge according to still another aspect of the present invention includes controlling a power level of the radio frequency signal applied to the plasma display panel to switch the radio frequency signal.
A driving circuit for a plasma display panel according to still another aspect of the present invention includes radio frequency generating means for generating a radio frequency signal to apply it to a radio frequency electrode of the plasma display panel; and switching means connected between other electrode of the plasma display panel connected to a ground line of the radio frequency generating means and the ground line to be switched in accordance with said interval of the radio frequency discharge, thereby controlling a power level of the radio frequency signal applied to the radio frequency electrode.
A method of controlling a plasma display panel device according to still another aspect of the present invention wherein an address discharge for selecting cells to be displayed is made by a current voltage applied to crossing electrodes while a sustaining discharge for sustaining said discharge of the selected cells to provide a display is made by a radio frequency voltage, includes turning on or off said radio frequency voltage with a switching pulse to be turned on only in the sustaining-discharge interval; and applying turning-on signal before the radio frequency signal is completely erased by applying a turning-off signal.